Composite drill pipe

ABSTRACT

A metal to composite tube joint including an elongated interior fitting constructed with an exterior barrel, reduced in exterior diameter to form a distally facing annular shoulder and then projecting still further distally to form an interior sleeve having a radially outwardly facing bonding surface. An elongated metal outer sleeve formed proximally with a collar constructed for receipt over the barrel and increased in interior diameter and projecting distally to form an exterior sleeve having a radially inwardly facing bonding surface cooperating with the first bonding surface to form an annulus receiving an extremity of a composite tube and a bond bonding the extremity of the tube to the bonding surfaces.

CROSS-REFERENCES TO RELATED APPLICATIONS

The teachings herein constitute continuation of U.S. patent applicationSer. No. 14/251,831 filed Apr. 14, 2014, which is a divisionalapplication of U.S. patent application Ser. No. 13/551,446 filed Jul.17, 2012, now U.S. Pat. No. 8,696,034, which is a continuation of U.S.patent application Ser. No. 13/342,952 filed Jan. 3, 2012, now U.S. Pat.No. 8,287,005, which is a continuation of U.S. patent application Ser.No. 12/323,067 filed Nov. 25, 2008, which is a continuation-in-part ofthe matter disclosed in U.S. patent application Ser. No. 10/952,135filed Sep. 28, 2004, now U.S. Pat. No. 7,458,617, and the benefit ofthese earlier filing dates being claimed and the content thereofincorporated herein by reference as though fully set forth hereon.

STATEMENT OF GOVERNMENT INTEREST

This invention was partly funded by the Government of the United Statesof America under Cooperative Agreement No. DE-FC26-99FT40262 awarded bythe U.S. Department of Energy and the Government of the United States ofAmerica has certain rights in the invention.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to composite torque tubes and the methodfor forming the same.

The Prior Art

Composite tubes have long been recognized for their light weight andtorque transmitting capabilities. To realize the full benefit of thetorque carrying capacity it is necessary that the remaining componentsof the torque transmitting string be especially strong.

The inherent difficulty in forming a high integrity interface between acomposite tube and the adjoining surfaces has long been recognized. Ithas been common practice to form a joint with a mutual fitting or sleevehaving a shell with a single surface abutting the wall of the compositetorque pipe. This arrangement provides a single interface for bonding,sometimes referred to as a single shear lap joint, a method of forming ajoint of this type is shown in U.S. Patent Appl. No. 2005/013783 toWilliams. These single lap joints fail to provide the integritynecessary to carry high torque loads without failure.

In the past, fitting assemblies with variously opposing surfacegeometries have been proposed to effect a secure capture of thecomposite end of a torque pipe within the fitting. Some examples ofmaking, such end fittings include those taught in U.S. Pat. No.4,421,497 to Fiderman; U.S. Pat. No. 5,233,737 to Policelli; U.S. Pat.No. 4,810,010 to Jones; U.S. Pat. No. 6,315,002 to Antal et al.; andothers. While suitable for the purposes intended each of the foregoingassemblies include threaded or otherwise releasably engaged partsclamping or compressing the composite between each other with inherentlyuneven load concentrations resulting in highly uneven shear stresses.This uneven load distribution between adjacent parts, of course, resultsin correspondingly uneven local strain deformations when exposed to thevarious high loadings in the course of use. There is therefore aninherent incidence of local bond separation between the composite itselfand the adjoining fitting surface, with some consequence for failure.

Artisans have recognized that the high torque loads applied to driveshafts cannot be adequately carried by previous proposals for wrappingfilament bundles around circumferential grooves on a sleeve peripheryand proposed a method for employing a tubular sleeve with longitudinalknurls, U.S. Pat. No. 4,238,539 to Yates. Devices by this method areexpensive to make and fail to provide the requisite load carryingcapability for many high torque applications.

Efforts to enhance joint strength have led to proposals that theinterference between an end fitting and pipe be splined or groovedlongitudinally or circumferentially for receipt as a bond. Approaches ofthis type are shown in U.S. Pat. No. 4,830,409 to Freeman, U.S. Pat. No.4,952,195 to Taylor and U.S. Pat. No. 5,601,494 to Duggar. Joints madeby these methods fail to provide smooth, uniform interfaces to enhancethe bond strength and distribute stress uniformly over the jointinterface.

Alternatively, end fitting assemblies have been proposed in which radialpins or other radial fasteners are added to the assembly, as exemplifiedby the teachings of U.S. Pat. No. 5,332,049 to Tew; U.S. Pat. No.5,288,109 to Auberon et al.; U.S. Pat. No. 5,443,099 to Chaussepied etal.; and others. Once again, while a change is realized from theseradial interconnections the essentially separated nature of a singlemetal to composite surface interface is also susceptible to uneven loadtransfer with the consequent local separations an inherent possibility.For example, the '049 patent to Tew appears to disclose a singlemetal-composite interface held together by radial pins and an adhesivebond which may suffer from disparate torsional forces. Tew appears topropose a cylindrical outer protective sheath drawn over the pipe andlacking a tapered surface interface and suffers the shortcoming that,the coupling itself fails to provide a high strength joint capable ofcarrying the high torsional force necessary to withstand the loads ofboth extended reach applications and short radius.

It can be seen then that a need exists for a lightweight and durablestructure capable of withstanding the rigors of deep and directionaldrilling.

SUMMARY OF THE INVENTION

Briefly and in general terms, in one aspect the present invention isdirected to a composite to metal joint for connecting composite torquepipe to a mechanical end fitting. The device is a metal inner sleeveconfigured with a barrel and sleeve projecting from an annular flange todefine on its exterior a distally narrowing conical shell surface. Oneend of an exterior sleeve is telescoped over the barrel and is formedwith a distally projecting outer shell formed with an interior smoothconical inner shell surface concentric with the inner shell itself andcooperating therewith to form an annulus distally expanding in radialthickness, a composite torque pipe is formed with an extremity formedwith a concentrically tapered connector ring configured to complimentthe shape of the annulus. The ring is inserted in the annulus and abonding material is applied to the interface between the sleeve surfacesand the connector ring and allowed to cure.

Other features and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings which illustrate, by way of example, the featuresof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective illustration, separated by parts, of aconventional drill pipe string extended into a well bore;

FIG. 2 is an exploded perspective illustration, partially in section, ofthe metal to composite end fitting assembly embodying the pipe assembly;

FIG. 3 is a further perspective illustration of the pipe assemblyincorporating the parts illustrated in FIG. 2;

FIG. 4 is a sectional view, of a coupled pipe joint illustrating thesignal connection between pipe parts shown in FIG. 2;

FIG. 5 is an enlarged end view taken along the line 5-5 shown in FIG. 4.

FIG. 6 is an enlarged end view taken along the line 6-6 shown in FIG. 4.

FIG. 7 is a side view, enlarged of the circle shown in FIG. 4.

FIG. 8 is a side view, enlarged of the circle shown in FIG. 4.

FIG. 9 is a perspective illustration, in partial section, of the toolingarrangement useful in combining the inventive assembly into an integralfixture;

FIG. 10 is a diagrammatic view, in perspective, illustrating theinventive implementation of a forming facility useful in forming thecomposite pipe segment on a rotary mount incorporating portions of theend fitting assembly;

FIG. 11 is an enlarged cross sectional end view taken along the line11-11 of FIG. 10;

FIG. 12 is a sequence diagram of an end fitting assembly sequence inaccordance with the present invention;

FIG. 13 is a perspective exploded illustration, of a second embodimentof the metal to composite end fitting of the present invention andshowing an electrical contact mechanism bridging electrical conductionacross a threaded pipe joint;

FIG. 14 is an enlarged sectional detail view of the contact mechanismshown generally in FIG. 13 before the full threaded engagement of a pipejoint;

FIG. 15 is an enlarged sectional detail view of the contact mechanismshown generally in FIG. 13 after the full threaded engagement of a pipejoint;

FIG. 16 is a side cross sectional view of the threaded joint interfaceand contact mechanism shown generally in FIG. 13;

FIG. 17 is a broken longitudinal sectional view of a third embodiment ofthe pipe assembly shown in FIG. 3; and

FIG. 18 is a detailed view in enlarged scale taken from the circle 18shown in FIG. 17.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1 current drilling practices depend on a string SPcomposed of drill pipe segments PS connected end-to-end to turn acutting tool CT mounted on the lower string end. In the course of suchturning, the tool CT grinds and penetrates through the bottom of thewell bore WB with the particulates continuously brought out to thesurface by a circulating flow of drilling mud DM pumped into the bore toequalize bore pressures. As readily available formations are depletedthese drilling projects now extend to much greater depth, and/or greaterlateral reach, with the weight of the pipe string SP and/or its frictionload in the well bore setting the practical exploration limits. Thecomplexity of a drilling rig RG conformed for such long reach drillingis enormous and the logistics of its movement alone, encouragedirectional capability along with an increasing pipe string. This samecomplexity of the rig also determines the manipulation convenience ofeach of the pipe segments PS, again resulting in its own logistic andmechanical constraints resolved by the size of the rig (or off-shoreplatform) that can be effectively implemented at the well site, therebylimiting the length of each segment PS and multiplying the number ofrequired joints JT that need to be made to extend the string to thedesired depth. The combined weight of the string, including all the downhole joints and any wear knots or pipe protectors 90 shielding the pipefrom wall contact, along with the friction load resulting from this wallcontact, are thus resolved at the last surface joint which sets thedesign limit. It is within this limit that the rig operator tries todiscover oil by periodic insertion of instruments down the bore, orsimply by inspecting the drilling debris brought to the surface.

In addition to the above physical concerns there are also those imposedby various laws and ordinances dealing with the environment. There iscurrently substantial public resistance to the equipment clutterassociated with crude oil production appearing in one's neighborhood,further promoting directional drilling, a technique that compoundstorsional loading as very long drill pipe strings are turned whileresting on the wall of the well. This same technique also demandsshorter radius turns, or a more flexible pipe, and also accurateinstrumentation to inform the operator of the actual direction that isbeing drilled and of any formation details that are encountered. For allthese reasons light weight, high strength, but elastic pipe is desired,particularly if signal and power conductors can be combined therewith.All these concerns are now substantially resolved in the inventivestructure and process described by reference to FIGS. 2-18.

By particular reference to FIGS. 2-4 one aspect of the inventive pipeassembly, generally designated by the numeral 10, comprises a tubularcomposite pipe segment 11, formed by winding up reinforcing fiber, suchas carbon fiber, preferably wound in stress determined orientationpatterns between plies of interleaved wrapping, all bonded together byresinous filler to form a cylindrical structure of a generally uniformwall thickness over most of its length.

Pipe segment 11 may be formed with a generally uniform taper along aselected portion of each end 12-1 and 12-2 reducing in wall thickness.Each end may be defined by interior and exterior wall surfaces 12 i and12 e respectively, that are configured for receipt within conformingannular cavities formed by male and female couplers comprising a set ofnested metallic end fittings 20-1 and 20-2 and metallic sleeves 30-1 and30-2. Those skilled in the art will appreciate that the surfaces of thepipe segment and adjoining structures for that matter, may use othersurface configurations, yet, in one embodiment, tapered andfrustoconical surfaces are used permitting a diffusion of torsionalloads across the surfaces of connected pieces.

The metallic end fittings 20-1 and 20-2 include a flange 29 withshoulders 29-1 and 29-2 and skirt 23 including an exterior surface 22 etapering in reducing cross section away from the flange.

The metallic sleeves 30-1 and 30-2 include respective telescopingflanges 39 and skirts 33 formed with interior surfaces 32 i tapering andexpanding cross section away from the flange to, when assembled with therespective fittings 20-1 and 20-2 cooperate in defining an annulusdistally expanding in thickness (FIG. 9).

The annular cavities formed by the nested pieces are formed by axiallyaligning the tapered exterior surface 22 e of skirt 23 adjacent anoppositely tapered surface 32 i on the skirt 33 interior. The surfaces22 e and 32 i are each closely matched to respective dimensions andtapered surfaces 12 e and 12 i where insertion of the surfaces 12 e and12 i into the annular cavity forms an aligned pipe segment endinterface. Those skilled in the art will appreciate that thisself-aligning construction creates a bonding interface that can beeffected by any high temperature epoxy resin and will further appreciatethat the close fit of this bond is further enhanced by close dimensionalmatching between the coaxially nested end fitting and sleeve pieces sothat the sleeve forms a peripheral support for the tapered end of thepipe segment as it is slid into position within the end fitting.

In addition, each of the skirts 23 and 33, moreover, may include aradially matched set of lateral openings 24 and 34 dimensioned for pressfit or interference receipt of corresponding optionally used pins 45that also pass through corresponding circular openings 15 formed in thetapered ends 12-1 and 12-2 once the ends are fully received, bonded andindexed within their receiving cavities. This same indexed alignment mayorient the exposed ends 18 of conductor leads 17 that are woven into thefilament matrix of the pipe segment 11 into alignment with longitudinaldrillings 37 formed in skirts 33 to effect an electrical connectionacross the pipe joint herein described. Beyond this bonding receipt,each of the pieces is formed as a closely dimensioned telescopingcylindrical segments 26 and 36 which are each provided withcorresponding exterior flanges 29 and 39 aligned next to each other whenthe skirts are properly positioned. Of course, the same drillings 37extend through the flange 39 to convey the lead ends 18 there-through.

Those skilled in the art will appreciate that while pieces 20-1 and20-2, and also pieces 30-1 and 30-2, are described above by identicaldescriptions, in application one of the nested end piece sets serves asthe male portion of the threaded joint, otherwise referred to as the‘pin end’, and the other end piece set serves as the female threaded, orthe ‘box end’. Accordingly, those parts of the end fitting pieces 20-1and 20-2 that are exterior of flanges 29 are of necessity differentdepending on the joint function that is formed. Thus end fitting 20-1includes a threaded boss 51-1 extending beyond the exterior shoulder29-1 of the flange 29 that is conformed for threaded receipt in athreaded cavity 51-2 formed in the other exterior shoulder 29-2 of theother flange 29 on the end fitting piece 20-2. Each of the flanges 29,moreover, includes drilling continuations shown as drillings 27-1 and27-2 (FIG. 4) aligned with drillings 37, drilling 27-1 conveying theconductor end 18 into a circular recess 53-1 formed in the flangeshoulder surface 29-1 where the lead is connected to an insulated ring54-1 conformed for receipt within the interior of recess 53-1.

In an exemplary assembly, the overall length of the pipe assembly 10measures approximately 359 inches. In this assembly, the composite pipe11 measures 338.00 inches long between respective outer sleeve proximalends 30-1 and 30-2 and includes an inner diameter of 1.625 inches and anouter diameter of 2.510 inches intermediate the end assemblies. Thediameters expand outwardly therefrom toward the assembly fittings wherethe pipe inner surface 12 i and exterior surface 12 e respectively areformed with radial dimensions matching their confrontment with endfitting exterior surface 22 e and sleeve inner surface 32 irespectively. The overall pipe string diameter expands from thecomposite pipe 11 outer diameter of 2.510 inches to a metallic fittingend diameter of 3.405 inches. The length of the “pin” end assemblymeasures approximately 10.00 inches from the distal end of male boss51-1 to the outer sleeve 30-1 proximal end. The “box” end assemblymeasures approximately 1.00 inch longer between respective like featuresof female boss 51-2 and sleeve end 30-2 to accommodate the male boss51-1. Thus, it will be appreciated that the metal to compositeconjunction is useful in extended reach applications by providing adiffusion of loads across the joint interface.

During operation in extended reach drilling applications, as pipestrings drill deeper into earth using longer strings, the greater theweight of the string becomes, thus promoting drag and inhibitingdrilling performance and efficiency. Greater weight contributes toincreasing tensile strength loads under the increasing pressures of deepextended reach drilling environments pulling and stretching on the pipeassembly components, and in particular, tugging on joints where tensileloads can separate parts. As will be appreciated, the length of thedrill string of the presently described embodiment is approximately 86%composite material length compared to approximately 14% metallicmaterial length. The metal is primarily reserved for the end fittings 20and sleeves 30 that support the joint interface to the composite pipesegment 11 and provide strengthened joint coupling between adjacent pipeassemblies where tensile loads can do significant harm. Furthermore, toaid in drilling extended distances, it will be understood that as thecomposite layers are formed, additional carbon material may be added tostrengthen the tensile load capacity of drill strings. The compositepipe 11 walls may also be conveniently adjusted to thicker or thinnerthicknesses depending on the depth of drilling by forming the pipesegments with more or less composite layers.

It will be appreciated that the drill string is conducive to carryingtorsional loads by both the internal fitting to composite wall interfaceand by the metallic outer sleeve. In operation, as the drill pipe stringturns, force loads are distributed along the walls of the drill pipeassembly and are diffused over pipe walls expanding from theintermediate portion toward the joint assembly interfaces and ends. Whenloads propagate toward the joint assemblies, these loads encounter thedual tapered surface interface between the metallic end fittings 20 andmetallic sleeves 30 confronting the composite pipe disposedintermediately there-between distributing the loads across two surfacesinterfaces. As torsional forces encounter the first tapered interfacebetween the metallic end fitting and composite pipe, the taperedsurfaces create a larger area of load confrontment thereby diffusing theload effects over a greater surface area. Those skilled will appreciatethat this effect is enhanced by a second tapered interface between thecomposite pipe and sleeve tapered surfaces where the loads once againencounter an extended surface area diffusing the loads a second time asthe outer sleeve carries part of the load. As such, drill assemblies forlong reach with the proposed configuration can be assembled in stringsbeyond 35,000 feet in length.

Referring to FIGS. 5-8, end fitting 20-2 includes a drilling 27-2indexed with drilling 37 in the sleeve 30-2 to convey the otherconductor end 18 into a manifold 56 (FIG. 8) formed in flange 29 andterminating in one or more openings 57 through shoulder surface 29-2opposing the recess 53-1 when the ends are threadably mated. Opening 57,may in turn, be provided with a spring biased piston 58 carrying abayonet point 59. Referring to FIG. 5, a sectional end view of the “pin”end is illustrated showing the insulated contact ring 54-1 circumscribedwithin the circular recess within the flange 29-1. The assembly ofcircular features in FIG. 5 are shown in relation to the features ofFIG. 6 where the spring-biased piston and bayonet point on the “box” endin manifold 56 are in circumferential alignment to the ring. Once thebosses 51-1 and 51-2 are joined together, it is then useful topressurize the manifold interior, advancing the piston against thespring bias to drive the bayonet point through the insulation on theopposingly aligned contact ring. In this manner, one example of circuitcontinuity is effected between the conductors 17 imbedded in the joinedsegments regardless of their relative orientation.

Those in the art will further appreciate that the foregoing arrangementsare particularly suited for custom forming of composite pipe segments 10by way of the nested end fittings described herein. By particularreference to FIGS. 9-12, the fitting end pieces 20-1 and 20-2 may becombined with a forming mandrel effected by an inner core layer 111(FIG. 10), to form the turning core for the subsequent winding of fiberplies 92 and the remaining interleaved layers 93 forming the compositepipe 11, in step 201. In this step the winding pitch, fiber density andthe selection of any sealing wraps may also be determined by theparticular parameters of the well and the mandrel structure may befurther stiffened and assisted by internal pressurization while thefiber wind-up tension is controlled. Of course, conductive leads 17 maybe concurrently also imbedded into the wrap, again in accordance withthe type and nature of the signals and/or power that may be conveyedthereon. Once the structural conditions are met the end fittings arewithdrawn from the core layer and thereafter nested in the sleeve pieces30-1 and 30-2 in step 202.

A bonding agent, such as a high temperature epoxy resin is then appliedto the pipe ends tapered rings defining the pipe ends 12-1 and 12-2 andthe ends are then re-positioned into the interiors of sleeve pieces 30-1and 30-2 with the end fitting pieces 20-1 and 20-2 then pressed intotheir common interiors, shown as the self-centralizing step 203. In thecourse of this same step the exposed conductor ends 18 are conveyed intotheir appropriate drillings to be thereafter connected either to thebayonet contact 59 or the contact ring 54-1. In step 204 the foregoingassembly is then brought into a spray cooled welding fixture illustratedin FIG. 9 in which a weld 91 is applied by a welding device 151 to jointhe exterior flanges of the nested pieces 20-1 and 30-1 to each other(and by the same example also the nested pieces 20-2 and 30-2) whilewater spray heads 152 and 153 cool the adjacent structure. Optionally,once fixed by their flanges, the sleeve and end pieces, with the ends12-1 and 12-2 captured there-between, are then drilled, in step 205,with perforations 34 which thereafter receive press fit pins 45.

In this manner a self-centralized end arrangement is useful both in themanufacturing and also in effecting a closely held bond interfacebetween the high strength metal end pieces and the composite pipesegment with the interface further stabilized and fixed by welding andpress fit pins. Simultaneously, this manner of manufacture also providesa durable, convenient and effective manner of incorporating a conductorinto the pipe fully protected by the pipe pieces. The resulting highstrength joint is then further complemented by the appropriatelyselected wind-up pitch, weave density and interleaving that are selectedfor the particular task. Thus, the fabrication and the ending structureare rendered both highly effective and convenient.

It will also be appreciated that the aforedescribed drill pipe stringmay be improved upon to include enhanced configurations for effecting anelectrical connection along the pipe string and modifications to thecomposite-metal interface providing a durable yet flexible structureconducive to short radius drilling.

By reference to FIGS. 13-16, a second preferred embodiment employs theinterior and exterior distantly converging tapered surfaces at theopposite extremities of the composite segments 11 and showing analternative contact implementation is obtained by embedding coaxialcontact rings in each of the opposing shoulder surfaces 29-1 and 29-2surrounding both the ‘pin’ end and the ‘box’ end of the joint assembly.As will be appreciated by those skilled in the art, one or the other orboth of the tapers may be in the form of continuous smooth surfaces asshown in FIGS. 2 and 16 or in some instances in the form of steppedsurfaces cooperating to progressively narrow the thickness of thesegment wall in the distal direction. Once again, like numbered partsfunctioning in a manner like that previously described are utilizedexcept that shoulder surfaces 29-1 and 29-2 are each provided with anannular groove 53-1 and 53-2 of a sectional dimension conformed toreceive a corresponding elastomeric annular seal 255-1 and 255-2. Seal255-1 is generally shaped as a U sectioned structure defined byconcentric inner and outer annular walls 256 i and 256 o extending froma bottom wall 257. A conforming contact ring 261 chamfered along itsupper edges by a peripheral chamfer 261 e is then captured by elasticstretching within the annular cavity 256 formed between the inner andouter sealing walls 256 i and 256 o of the seal 255-1 with the outerwall stretching just over the chamfer to retain the ring in position. Asimilarly dimensioned contact ring 262 is then received in the annularcavity 258 formed between the inner and outer walls 258 i and 258 o ofthe ‘box’ end seal 255-2, with the groove depth (or wall height) ofwalls 258 i and 258 o being substantially greater than the thickness ofthe ring 261 and 262 and the depth of the receiving recess 53-2. Theheight of seal 255-1, in turn, is somewhat less than its receivingrecess 53-1. Preferably, both the contact rings 261 and 262 are insertedwithin their respective seals so that each contact surface projects justslightly above the corresponding surface 29-1 and 29-2, a projectiondetermined by the dimensions of the annular recesses or grooves 53-1 and53-2 and the dimensions of each seal. Of course, walls 258 i and 258 oeach project beyond the corresponding surface of ring 262 before thethreaded engagement of the joint, as illustrated in FIG. 14.

In this projecting deployment both the opposing seals and the ringsseated therein are fixed in rotation in each corresponding recess 53-1and 53-2 by way of spaced axial pins 263 and 264 that project from theburied edges of each of the rings 261 and 262 into conforming pockets259 in each of the seal bottoms which are then inserted into conformingcavities 269 formed in the abutment surface bottoms of each of therecesses 53-1 and 53-2 (FIG. 13). The projecting seal edges and therings therein therefore slide in rotation relative each other as thepipe joint is made. As illustrated in FIG. 15, once the joint is made,the excess volume of the elastomeric matter forming each of the sealwalls 258 i and 258 o fills the volume of the concentric annularopen-ended grooves defined by the respective edge chamfers 261 e whichalso assist in the spreading of the seat edges to facilitate a directcontact between the rings as illustrated before the mating in FIG. 14.Thus the edge chamfers in ring 261 allow for the elastomeric materialflow of the seal material as the joint is threaded together, ensuring acompletely surrounding sealing closure as the exposed edges of the ringsare pressed against each other while the smaller contact dimensionformed between the edge chamfers 261 e assures a better ring contactwhile also accommodating a somewhat less precise axial registrationbetween the pipe segments. This same material flow may be utilized toboth seal and capture the exterior insulation 275 e around a conductor275 extending through corresponding drillings 271-1 and 271-2 throughcorresponding shoulders 38-1 and 38-2 and extending into one of thecavities 269 in the bottoms of recesses 53-1 and 53-2 to pass therespective lead ends 275 through the seal material and thereafter intoperforations 261 p and 262 p in the corresponding rings 261 and 262.Referring to FIG. 16, a return conductor 285 connected directly betweenthe pipe segment ends can then be utilized to provide the return orcommon ground. Thus, when environmental resistance is encountered atcertain depths, the load carrying capacities of the drill stringsections can be adjusted accordingly. In this manner, a rugged andreliable contact is effected, thus accommodating both the power and thesignal needs in deep well drilling.

In operation, threaded assemblies may not result in the same two polarpoints aligning functionally. It may occur that a point on a threadedend does not meet a corresponding point on a receiving end more thanonce because the boss end may begin at a different point for threadingor the degree of torque applied at the end of the threading shifts thepoints. Those skilled in the art will appreciate that by utilizingcontact rings at the end fittings of a threaded pipe assembly, aneffective and efficient means for conduction of a signal is maintainedeven where the conductors are not in direct contact or alignment to oneanother. It will be seen that the contact rings 262 and 261 will be inconductive engagement regardless of where the conductor 275 is situatedon one end piece after threading relative to where the next conductor275 is on an adjacent segment. Thus, as long as the contact rings areengaged and the conductors are in conductive proximity to the axial pins263 of their respective contact ring and insulated from electricaldiffusion from one another and the surrounding conductive elements,signal can be successfully transmitted from one conductor through thecontact ring conjunction to the next conductor.

It will also be appreciated that by using annular seals 255 toincorporate the contact rings 261 and 262, an efficient means ofmaintaining the conductive integrity is preserved. The annular sealassists in protecting the contact ring from the conductive propertiesand stress imposed by the metal walls of the pipe end fittings. Bysheathing the conductor in an insulation 275 e in conjunction withhousing the contact rings in the annular seals, signal loss may beprevented from escaping to the pipe exterior. Once the two pipe ends arepress fit, further insulation is achieved where the elastomeric flowfills the annular voids within the shoulders 29 of the two ends. Byinsulating the conductive components of the contact rings from otherconductive components, a signal can be transmitted down a line withoutshort. Additionally, as the pipe assembly advances through jagged rocksurfaces contacting the drill pipe outer walls, it will be furtherappreciated that embedding the conductor 275 into the composite pipesegment walls and subsequently into the sleeves 30 and end fittings 20protects the conductor from frictional contact with the surroundingenvironment.

It will be further appreciated that each of the conductors may bevariously effected either as an electrical power lead, a signal lead oreven a fiber optic filament. Of course, known techniques of signalsuperposition, frequency and/or pulse modulation or other signalingformats can then be effected by these leads to bring out down holeinformation directly to the rig operator as the drilling is taking placewhich can then be used to modify, in known techniques, the drillingdirection and the cutting rate, commonly referred to as LWD or ‘loggingwhile drilling’ and MWD or ‘measuring while drilling.’ In this manner,all the control and pipe compliance conditions can be convenientlyaccommodated in a pipe string that, because of its light weight, isparticularly suited for ultra deep and/or extended reach drilling.

In a third preferred embodiment, it will be understood that for shortradius drilling applications such as from offshore oil platforms wherethe drilling direction is rapidly changed to avoid obstructions or basedon a feedback signal, the nested pieces and their respective taperedsurfaces may be modified to withstand varying external loads on the pipejoints accommodating flexing during drilling while maintaining ametal-composite interface conducive for carrying a torsional loadcapacity. For example, the drill string configuration 300 in FIGS. 17and 18 is similar to the drill string embodiment shown in FIGS. 2-4except that the longitudinal length of the inner annular sleeves 323 ofthe metal end fittings 320-1 and 323 are concentric with and projectapproximately 1 inch beyond the end of the respective outer sleeves330-2 facilitating flexure at the metal-composite junction. Similar tothe embodiment shown in FIGS. 2-4, ends 320 and 330 include the innerand outer annular shells 320-1 and 320-2, respectively, formed with therespective concentric annular sleeves 323 and 330-2 defining respectiveconcentric, annular, confronting, tapered surfaces 332 i and 312 eexpanding distally away from one another to form a conical annularnesting cavity for bonded receipt of tapered surfaces 312 i and 312 e ofrespective pipe segment bonding rings 312-1 and 312-2.

Referring to FIG. 17, the end fitting 320-1 is configured with anannular exterior flange 329-1 formed with a first distally facingannular stop shoulder 329-5 and then projects distally to form anannular radially outwardly projecting flange defining a barrel 329-2 andis then stepped down further in diameter to form a second distallyfacing annular abutment shoulder 329-3 spaced from the shoulder 329-5and then projects distally to form the shell 323, terminating in adistal extremity 328-2. Additionally, those skilled will recognize thatthe composite pipe segment 311 can be constructed to include less carbonmaterial providing more flexibility in the composite segment length.Thus, it will be appreciated that the pipe assembly 300 is conducive forproviding quick turns while maintaining durable integrity duringadvancement of drilling.

The outer sleeve 330-2 is configured with a cylindrical outer surfaceand is formed proximally with an interior cylindrical, stepped down indiameter to form a cylindrically radially inwardly projecting flangedefining a collar 330-3 to fit over the barrel 329-2 and is stepped upin diameter to form a distally facing abutment shoulder 329-4 alignedwith the shoulder 329-3 to form a combined annular shoulder againstwhich the blunt end of the respective pipe segment rings 312-1 and 312-2are abutted. The inner sleeve terminates in an extremity projectingdistally beyond the distal extremity 338-1 of the outer sleeve. In oneembodiment, a weld nut is provided to weld the proximal end of the outersleeve to the first annular shoulder. The fitting 320 is configured atits proximal end with a boss 320-1 formed with a threaded nipple 320-1.The fitting 320-2 is formed with an internally threaded box 351-2. Abond 338-2 is received in the interface between the outside surface ofthe pipe 311 and the inner surface 312 e and a second bond at theinterface between the exterior surface of the pipe and the interiorsleeve surface 332 i.

In operation, as the drill assembly 300 rotates advancing toward an oiltrap, the composite walls and offset metallic end portions provide aflexure point at the metal-composite interface facilitating directionalchange during short radius turns. Those skilled will recognize that thecomposite pipe walls are relatively more flexible than the metal endfittings. Thus, upon a relatively rapid change in drilling direction,the composite walls will bend in the direction of the turn and theinternal metallic fitting end bends with the composite walls. Theexternal metallic sleeve end, in turn, provides a flex point for theinternal metal end fitting and composite wall to bend from whilesimultaneously supporting the metal-composite joint interface topartially carry torsional loads. As portions of the string advance pastshort radius turns, the bending loads on the composite walls lessen andthe more rigid metal end fitting helps draw the composite walls back toa linear state. Similar to the embodiment shown in FIGS. 2-4, as loadspropagate down the drill string and encounter the metallic-compositejoint interface, torsional loads once again encounter two extendedcross-sectional areas between the metal and composite surfaces and thus,diffuse the loads at the two interfaces. Thus, an appreciable degree offlexibility may be achieved during short radius drilling while providinga durable structure that can return to is rigidity as the pipe string isextracted from its hole.

It will also be recognized that the drilling experience is furtherenhanced by incorporating the conductor 275 to the pipe assembly 300without detracting from the efficiency of or compromising the integrityof the assembly structure. As a string travels deeper into earth and theloads continue to mount on the string structure, it will be appreciatedthat measuring signals sent along the string via the conductor 275 canprovide feedback for adjusting rotational speed as well as update thecomposition of surrounding geological attributes relative to oilproximity. The flexibility of the conductor cooperates with theadvancement of the pipe assembly 300, particularly in short radiusapplications where the conductor can flex right along with the pipesegment during tight turns.

The invention may be embodied in other forms without departure from thespirit and essential characteristics thereof. The embodiments describedtherefore are to be considered in all respects as illustrative notrestrictive. Although the present invention has been described in termsof certain preferred embodiments, other embodiments that are apparent tothose of ordinary skill in the art are also within the scope of theinvention. Accordingly, the scope of the invention is intended to bedefined only by reference to the appended claims.

We claim:
 1. A metal to composite tube joint, including: an end fittingconfigured with an exterior flange having a first outer radius, a barreldistal to the exterior flange and having a second outer radius less thanthe first outer radius defining a first distally facing annular shoulderat a juncture of the exterior flange and the barrel, the barrelterminating at a distal end to define a second annular shoulder, aninner sleeve projecting further distally to form an inner shell defininga frustoconical outwardly facing bonding surface; an outer sleeve, theouter sleeve formed proximally with an annular abutment end bearingagainst the first distally facing annular shoulder, and further formedwith a collar fitting over the barrel, and further distally formed withan increased inner radius to form a distally facing abutment shoulder,and still further projecting distally to form an outer shell having aradially inwardly facing bonding surface cooperating with the radiallyoutwardly facing bonding surface to form an annulus therebetween thatexpands distally from the distally facing abutment shoulder to a distalend of the outer sleeve; a composite tube constructed with an extremityof reducing thickness in a distal to proximal direction and adapted toconform to and be received in the annulus formed with the inner andouter bonding surfaces; and a bond on the inner and outer surfaces ofthe extremity to bond to the respective radially inner and outer facingbonding surfaces.
 2. The joint of claim 1 that includes: a bond on theinterface between the barrel and collar.
 3. The joint of claim 1 thatincludes: a weld welding the collar to the flange.
 4. The joint of claim1 that includes: the extremity with the outer surface tapering distallyoutwardly.
 5. The joint of claim 1 that includes: the extremity with theinner surface tapering distally inwardly.
 6. The metal to composite tubejoint of claim 1, wherein the composite tube includes a bonding ringreceived in the annulus, the bonding ring formed with a blunt tube endabutted against the inner and outer sleeves.
 7. The metal to compositetube joint of claim 1, further comprising a pin connecting the innersleeve and the outer sleeve and passing through the composite tube.